1. Field of the Invention
The present invention pertains to a laser-based system and, more particularly, to a laser-based system with laser detection and ranging (“LADAR”) and semi-active laser (“SAL”) system capabilities.
2. Description of the Related Art
A need of great importance in military and some civilian remote sensing operations is the ability to quickly detect and identify objects, frequently referred to as “targets,” in a “field of regard.” A common problem in military operations, for example, is to detect and identify targets, such as tanks, vehicles, guns, and similar items, which have been camouflaged or which are operating at night or in foggy weather. It is important in many instances to be able to distinguish reliably between enemy and friendly forces. As the pace of battlefield operations increases, so does the need for quick and accurate identification of potential targets as friend or foe and as a target or not.
Remote sensing techniques for identifying targets have existed for many years. For instance, in World War II, the British developed and utilized radio detection and ranging (“RADAR”) systems for identifying the incoming planes of the German Luftwaffe. RADAR uses radio waves to locate objects at great distances even in bad weather or in total darkness. Sound navigation and ranging (“SONAR”) has found similar utility and application in environments where signals propagate through water, as opposed to the atmosphere. While RADAR and SONAR have proven quite effective in many areas, they are inherently limited by a number of factors. For instance, RADAR is limited because of its use of radio frequency signals and the size of the resultant antennas used to transmit and receive such signals. Sonar suffers similar types of limitations. Thus, alternative technologies have been developed and deployed.
One such alternative technology is laser detection and ranging (“LADAR”). Similar to RADAR systems, which transmit and receive radio waves to and reflected from objects, LADAR systems transmit laser beams and receive reflections from targets. Because of the short wavelengths associated with laser beam transmissions, LADAR data exhibits much greater resolution than RADAR data. Typically, a LADAR system creates a three-dimensional (“3-D”) image in which each datum, or “pixel”, comprises an (x,y) coordinate and associated range for the point of reflection.
Laser energy also finds application in these kinds of environments in what is known as a semi-active laser (“SAL”) system. With the SAL system, a narrow laser beam is produced and transmitted toward a target. The laser radiation is typically generated and transmitted from a laser designator aircraft manned by a forward operator. The operator directs the laser radiation to a selected target, thereby designating the target. The laser radiation reflected from the target can then be detected by the laser seeker head of a missile or other weapon located remote from both the target and the laser energy transmitter. The SAL system includes processing equipment for generating guidance commands to the missile derived from the sensed laser radiation as it is reflected from the target. Such a system can be used by pilots or other users to identify a target and guide the missile or weapon to the target.
However, LADAR and SAL technologies typically are not deployed together. For one thing, the LADAR signal, its generation, and its transmission usually are not suitable for target designation, or “spotting.” U.S. Pat. No. 6,262,800, entitled “Dual mode semi-active laser/laser radar seeker”, issued Jul. 17, 2001, to Lockheed Martin Corporation as assignee of the inventor Lewis G. Minor documents one effort at combining the two technologies. In this patent, the LADAR transceiver is modified to be used as a SAL receiver as well as a LADAR receiver. However, the sensor disclosed and claimed therein still includes no on-board designator such that it must rely on a third party designator in the same manner as conventional SAL systems.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.